This invention relates to a seat belt device in an automobile, and more particularly to an adjustable shoulder anchor device which is mounted on a center pillar, and fixes a shoulder belt anchor.
One known example of a conventional seat belt devices for safely holding a passenger or the like within a vehicle on a seat is a three-point seat belt device using a continuous webbing.
In a seat belt device of this kind, as shown in FIG. 23, one end portion of a webbing 22 is retained by a retractor (take-up device) 27, and the other end is passed through a through anchor 23, and is retained by an anchor plate 28 pivotally mounted on a lower end portion of a center pillar 29. A through tongue 24 is mounted on the webbing intermediate the anchor plate 28 and the through anchor 23, and by engaging this through tongue 24 in a buckle 25 mounted upright at a generally central portion of a vehicle, the passenger can be held on a seat 30.
In order that the effective length of the webbing 22 is adjusted in accordance with the body physique/constitution of the passenger and that the webbing 22 is accurately put on the shoulder of the passenger, such a three-point seat belt device further employs an adjustable shoulder anchor device 31 for allowing the through anchor 23 (mounted on the center pillar 29) to move upward and downward so as to adjust the height of support of the shoulder belt.
In an adjustable shoulder anchor device (hereinafter referred to as "anchor device") of a seat belt device in an automobile, the height of support of the shoulder belt is adjusted in accordance with the body build and so on of the passenger.
When the automobile collides, an impact load and a tensile load are applied to the through anchor and an adjustable base fixing this through anchor in such a manner that the position of the through anchor can be adjusted.
In order to protect the passenger striking against the anchor device, for example, in a side collision of the automobile, the anchor device has heretofore been required to be easily deformed upon application of an impact load. The anchor device has also been required to well withstand a tensile load so that the ability of the seat belt to hold the passenger can be enhanced.
The conventional adjustable bases are classified into a channel type and a flat plate type.
The channel-type adjustable base has a channel-shaped (i.e., generally C-shaped) cross-section throughout the length thereof from one end to the other end, and fixing portions (fixedly secured to the center pillar), provided respectively at the opposite ends of this adjustable base, have also a channel-shape. The channel-type adjustable base is high in rigidity, and therefore has a high strength against both of an impact load and a tensile load. Since the adjustable base has a high strength against a tensile load, it is less liable to be deformed under a tensile load, for example, upon collision of an automobile, and therefore this enhances the ability of holding the passenger. However, since the adjustable base has a high strength against an impact load means that its ability to cushion an impact load is low, and therefore when part of the passenger's body strikes against the anchor device, an impact, applied to the passenger, tends to be large.
The flat plate-type adjustable base is flat as a whole although fixing portions, provided respectively at opposite ends thereof, are slightly bent, and a shoulder belt anchor is fixedly secured to a central portion of this adjustable base. This flat plate-type adjustable base is lower in rigidity than the channel-type adjustable base, and therefore has a problem that it has a lower strength against both of an impact load and a tensile load as compared with the channel-type adjustable base. Since the adjustable base has a low strength against an impact load and a tensile load, it has a high ability of cushioning an impact load, and therefore can reduce an impact to be applied to the passenger. However, since this adjustable base also has a low strength against a tensile load, it can be easily deformed under a tensile load, which results in a possibility that the ability of holding the passenger is lower as compared with the channel-type adjustable base.
A conventional rail member can be buckled or deformed by an impact load, produced when the passenger strikes against an adjustable shoulder anchor device, for example, in a side collision of an automobile, and absorbs its energy, thereby securing the safety of the passenger.
Thus, upon application of an impact load, the rail member is buckled, bent or deformed at buckling portions to absorb the impact load. However, if an energy of a reaction force, tending to restore the rail member, is accumulated when the rail member absorbs the impact force, it is thought that an impact can be applied to the passenger when the rail member is restored under the influence of the reaction force.
Incidentally, U.S. Pat. No. 5,529,344 entitled "SEAT BELT DEVICE FOR AUTOMOBILE" discloses a conventional technique in which a slot is formed in each fixing portion of a rail member, and a bolt is passed through the slot, and is threaded into a center pillar, thereby fixing the rail member.
In this device, however, upon application of an impact load, an impact is absorbed in an amount corresponding to the amount of movement of the rail member along the slot, but after the rail member fully moves along the slot, so that the bolt abuts against an end of the slot, a reaction force energy, tending to restore the rail member, is accumulated. And besides, upon application (inputting) of a tensile load, the rail member is deformed in an amount corresponding to the length of the slot, and if the slot is so increased in size that the reaction force energy will not be accumulated, the amount of deformation is further increased.
As described above, the conventional anchor device, having the channel-type adjustable base, has a high strength against an impact load, but has a problem that its ability of cushioning the impact load is low, and the anchor device, having the flat plate-type adjustable base, has the high ability of cushioning an impact load, but has a problem that it has a low strength against a tensile load, and is liable to be deformed.
In addition, the conventional rail member is deformed upon application of an impact load thereto, and absorbs the impact load. However, if the energy of the reaction force, tending to restore the rail member, is accumulated, the impact due to this reaction force, which is applied to the passenger, becomes a problem. In the construction disclosed in the U.S. Pat. No. 5,529,344, the reaction force is liable to be accumulated, and the deformation amount is large when a tensile load is inputted. If the slot is increased in size so as not to accumulate the reaction force energy, the deformation amount is further increased.